Fin

ABSTRACT

A fin comprising a foot pocket, two ribs and a web portion is provided in this invention. The foot pocket has a surrounding portion and a base portion, which together define a foot receiving space. The surrounding portion has a plurality of first and second structures; the ribs extend forwards from two sides of the foot pocket respectively; and the web portion is formed between the two ribs. The first structures and the second structures are alternately arranged, and a first thickness of each of the first structures is thicker than a second thickness of each of the second structures. Thereby, the foot pocket of the fin is made flexible and elastic for swimmers or divers with different foot forms and sizes.

This application claims priority to Taiwan Patent Application No. 100213175 filed on Jul. 18, 2011 and Taiwan Patent Application No. 100220648 filed on Nov. 2, 2011.

CROSS-REFERENCES TO RELATED APPLICATIONS

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fin, and more particularly, to a fin in which a foot pocket comprises the structures of different thicknesses that are arranged alternately.

2. Descriptions of the Related Art Snorkeling and diving are both popular water sports. Various innovative technologies related to fins have been developed gradually in the art, especially, the development of a fin that is comfortable to wear and has a reasonable price.

Because different users have different foot forms and sizes, it is difficult for the same fin product to be suitable for the foot forms and sizes of all users. For this reason, some users may feel uncomfortable because the fin design does not completely fit their foot forms or sizes. That is, if a user has to buy a fin that does not completely fit his or her foot form or size due to the limited number of choices, then when the user wears the fin 1 (as shown in FIG. 1) to dive, it will be difficult for the foot pocket 11 of the fin 1 to fit closely around the foot of the user and a gap is formed between the foot pocket 11 and the foot of the user. Consequently, a great force must be applied by the user to control the fin during the water sport, which will cause unnecessary consumption of the physical strength of the user. Therefore, a fin that does not fit the foot of the user not only lowers the sport efficiency of the user in the diving sport, but also greatly reduces the comfort level of the user wearing the fin.

On the other hand, if fin products are developed in a multitude of sizes and styles to satisfy the needs of different foot forms and sizes, this can lead to increased manufacturing costs, which in turn, increases the prices of the fin products. Furthermore, the cost to the sellers to display and inventory the fin products are also increased due to the multitude of sizes and styles.

Accordingly, it is important to provide a fin that can be slightly stretched in an elastic way to be suitable for use with different foot forms and sizes. This can improve the comfort level of the user wearing the fin and make it convenient for the user to wear, while still avoiding the increase in cost due to the need of developing fins of a variety of sizes.

SUMMARY OF THE INVENTION

To overcome the aforesaid problems, an objective of the present invention is to provide a fin. By using structures of different thicknesses that are arranged alternately on the foot pocket of the fin, the foot pocket can deform elastically according to the different foot forms to closely fit the foot of the user. Therefore, the fin of the present invention is suitable for use with foot forms and sizes of different users, which can reduce the cost associated with the development of fins of a variety of sizes.

The present invention provides a fin, which comprises a foot pocket, two ribs and a web portion. The foot pocket has a surrounding portion and a base portion for defining a foot receiving space. The surrounding portion has a plurality of first structures and a plurality of second structures. The two ribs extend forwards from two sides of the foot pocket respectively. The web portion is formed between the two ribs. The first structures and the second structures are alternately arranged, and the first thickness of each of the first structures is thicker than the second thickness of each of the second structures.

The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a conventional fin;

FIG. 2 is a schematic perspective view of a fin according to a first embodiment of the present invention;

FIG. 3 is a partially enlarged view of the fin according to the first embodiment of the present invention;

FIG. 4 is a schematic perspective view of another implementation of the fin according to the first embodiment of the present invention;

FIG. 5 is a schematic perspective view of a fin according to a second embodiment of the present invention;

FIG. 6 is a schematic view of the fin according to the second embodiment of the present invention from another view angle;

FIG. 7 is a schematic perspective view of a fin according to a third embodiment of the present invention;

FIG. 8 is a schematic perspective view of a fin according to a fourth embodiment of the present invention;

FIG. 9A is a schematic view of a fin according to a fifth embodiment of the present invention;

FIG. 9B is another schematic view of the fin according to the fifth embodiment of the present invention;

FIG. 10A is a schematic view of a fin according to a sixth embodiment of the present invention; and

FIG. 10B is another schematic view of the fin according to the sixth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following descriptions, the present invention will be explained with reference to multiple embodiments thereof. However, the description of these embodiments is only to illustrate the technical contents and objectives and efficacies thereof of the present invention rather than to limit the present invention. It shall be appreciated that in the following embodiments and attached drawings, elements not directly related to the present invention are omitted from depiction; and the dimensional and positional relationships among individual elements in the attached drawings are illustrated only for the ease of understanding but not to limit the actual scale and size.

The first embodiment of the present invention is a fin 2. FIG. 2 illustrates a schematic perspective view of the fin 2. The fin 2 comprises a foot pocket 21, two ribs 23, a web portion 25 and a hollow portion 27.

With reference to FIG. 2 and FIG. 3, which is a partially enlarged view of a part of a surrounding portion 211 that is circled by a dashed ellipse in FIG. 2, the foot pocket 21 has a surrounding portion 211 and a base portion 213. The surrounding portion 211 is disposed around and above the base portion 213 so that the surrounding portion 211 and the base portion 213 together define a foot receiving space 215 for receiving the user's foot. In more detail, the surrounding portion 211 comprises a dorsum pedis area 2111, two ankle areas 2112, a heel area 2113, a plurality of first structures 2114 and a plurality of second structures 2115. The dorsum pedis area 2111 comprises a front end 2111 a and a rear end 2111 b. The front end 2111 a is disposed adjacent to the rear position of the hollow portion 27 to correspond to the user's toe, and is disposed opposite to the rear end 2111 b. The rear end 2111 b is connected to the two ankle areas 2112 of the surrounding portion 211; that is, the ankle areas 2112 extend backwards from two ends of the dorsum pedis area 2111 respectively and are connected to the heel area 2113 disposed opposite to one of the ends of the dorsum pedis area 2111. Therefore, the dorsum pedis area 2111, the ankle areas 2112 and the heel area 2113 of the surrounding portion 211 define the foot receiving space 215 together with the base portion 213.

The two ribs 23 extend forwards from two sides of the foot pocket 21 respectively, and the dimensions of the two ribs 23 decrease gradually as the distance from the foot pocket 21 increases. The web portion 25 is formed between the two ribs 23. The web portion 25 of this embodiment has a completely enclosed surface; and in other embodiments, the web portion 25 may also be formed with a plurality of holes to reduce the resistance in water. The hollow portion 27 is formed in front of the front end 2111 a of the surrounding portion 211. The hollow portion 27 is an apertured structure; that is, a front end of the foot receiving space 215 is apertured so that the water can be drained during the use of the fin. In other implementations, there is no limitation on the size, the form and the number of the hollow portion(s). It is also unnecessary to form the hollow portion symmetrically; and instead, the hollow portion may be adjusted according to the requirements on the products.

Hereinbelow, the detailed structures of the surrounding portion 211 will be further detailed.

With reference to FIG. 3, the first structures 2114 and the second structures 2115 are illustrated in detail therein. As shown, the first structures 2114 and the second structures 2115 in the form of long concave and convex straps are formed on an upper surface 2116 of the surrounding portion 211; and a lower surface 2117 of the surrounding portion 211 is a planar surface. Therefore, the user's foot will come into contact with this planar surface without feeling uncomfortable. The first structures 2114 and the second structures 2115 are alternately arranged. In addition, the first thickness of each of the first structures 2114 is thicker than the second thickness of each of the second structures 2115. In more detail, the first thickness ranges between 1 mm and 15 mm, the second thickness ranges between 0.5 mm and 5 mm, and the first thickness is 0.5 mm to 14.5 mm thicker than the second thickness.

The first structures 2114 and the second structures 2115 of this embodiment are formed on the front end 2111 a and the rear end 2111 b of the dorsum pedis area 2111, the two ankle areas 2112 and the heel area 2113. In this embodiment, the first structures 2114 and the second structures 2115 are both long straps, and are alternately disposed along a certain direction. The first structures 2114 and the second structures 2115 both intersect with a periphery of the surrounding portion 211, for example, include an approximately 90° angle or some other angle with the periphery of the surrounding portion 211; that is, for the user, the first structures 2114 and the second structures 2115 are alternating concave and convex stripes arranged in a longitudinal direction. In other implementations of this embodiment, other numbers of long-strap structures may be devised by people skilled in the art to adjust the overall stretchability and elasticity, with the number of the first structures 2114 of the long-strap form being no less than 2 and the number of the second structures 2115 of the long-strap form also being no less than 2.

As described above, the first structures 2114 and the second structures 2115 of this embodiment are formed on the front end 2111 a and the rear end 2111 b of the dorsum pedis area 2111, the two ankle areas 2112 and the heel area 2113 to impart the desired elasticity to the fin 3 so that it is convenient for the user to wear the fin 3. However, an example in which the first and second structures are formed on either the dorsum pedis area, the two ankle areas or the heel area may also be readily devised by people skilled in the art, for example a fin 3 shown in FIG. 4. In this example, the fin 3 also comprises a foot pocket 31, two ribs 33, a web portion 35 and a hollow portion 37. However, the first structures 3114 and second structures 3115 are formed on the outer surface of two ankle areas 3112.

The foot pocket (especially the surrounding portion) of the fin of the present invention is made of a soft material such as thermoplastic rubber (TPR), thermoplastic polyurethane (TPU), thermoplastic elastomer (TPE), polyvinyl chloride (PVC), Silicone Rubber, Natural Rubber, Ethylene Vinyl Acetate (EVA) or a combination thereof; however, those of ordinary skill in the art may use other materials instead, and no limitation is made thereon. In the practical process of manufacturing the fin, the foot pocket (including the surrounding portion and the base portion), the ribs and the web portion are all integrally formed, which makes it convenient to manufacture the fin. However, in other implementations, it is also possible to form one of the components first and then use injection molding to cover the component with other components; e.g., a relatively hard material is used to form the web portion and the ribs, and then a relative soft material is used, via injection molding, to cover the web portion and the ribs with the foot pockets.

However, this is not intended to limit that all the aforesaid components must be integrally formed together, and the components may also be formed in groups and then combined together.

The second embodiment of the present invention is also a fin 4. With reference to FIGS. 5 and 6, FIG. 5 is a schematic perspective view of the fin 4, while FIG. 6 is a top view of the fin 4. In this example, the fin 4 also has a foot pocket 41, two ribs 43, a web portion 45 and a hollow portion 47; and first structures 4114 and second structures 4115 of a surrounding portion (not shown) of the foot pocket 41 are also formed on the front end 4111 a and rear end 4111 b of the dorsum pedis area 4111, two ankle areas 4112 and a heel area 4113. Therefore, the technical features of this embodiment are mostly the same as those of the first embodiment of the present invention, and thus, the same technical features will not be further described herein. However, it shall be particularly appreciated that the second embodiment differs from the first embodiment mainly in that in the second embodiment, the two ankle areas 4112 that are originally intact are formed with two symmetric holes 4118 at positions corresponding to the inner-side projection and outer-side projection of the user's ankle respectively so that the user's ankle can project outwards from the fin 4 through the two holes 4118. In other implementations, there is no limitation on the positions, forms and number of the holes and it is also unnecessary to form the holes symmetrically or correspondingly in the two ankle areas. As a result, the holes may be adjusted according to the functional requirements or the overall style of the product.

The third embodiment of the present invention is also a fin 5. FIG. 7 illustrates a schematic perspective view of the fin 5. The fin 5 of the third embodiment also has a foot pocket 51, two ribs 53, a web portion 55 and a hollow portion 57. The first structures 5114 and second structures 5115 of a surrounding portion (not shown) of the foot pocket 51 are both formed on the front end 5111 a and rear end 5111 b of a dorsum pedis area 5111, two ankle areas 5112 and a heel area 5113. Therefore, the technical features of this embodiment are mostly the same as those of the first embodiment of the present invention, and thus, the same technical features will not be further described herein. However, it shall be particularly appreciated that the third embodiment differs from the first embodiment and the second embodiment mainly in that in the third embodiment, the vertical height of the two ankle areas 5112 and vertical height of the heel area 5113 define an altitude difference therebetween so that recesses are formed in the ankle areas 5112 along the lower edges of the inner-side projection and the outer-side projection of the user's ankle respectively. As a result, the forms of the ankle areas 5112 can conform to the user's foot to increase the stretchability of the fin 5, thereby making it convenient for the user to wear the fin 5 and improve the comfort level of the user wearing the fin 5. In other implementations, there is no limitation on the positions, the form and the number of recesses of the ankle areas. The recesses may be adjusted according to the functional requirements or the overall style of the product. In more detail, the altitude difference between the vertical height of the ankle areas 5112 and the vertical height of the heel area 5113 may be designed differently depending on the fins of different sizes. The altitude difference in the present invention is between 10 mm and 80 mm.

It shall be additionally appreciated that even if the fin of the present invention is not formed with holes at positions corresponding to the user's ankle or has no altitude difference formed between the ankle areas and the heel area, the foot pocket of the fin can still be stretched elastically by means of the difference in thickness between the first structures and the second structures to closely cover the user's ankle following the user's foot form.

The fourth embodiment of the present invention is also a fin 6. FIG. 8 illustrates a schematic perspective view of the fin 6. The fin 6 of the fourth embodiment also has a foot pocket 61, two ribs 63, a web portion 65 and a hollow portion 67. Therefore, the technical features of this embodiment are mostly the same as those of the first embodiment of the present invention, and thus, the same technical features will not be further described herein. However, it shall be particularly appreciated that the fourth embodiment differs from the other embodiments mainly in that in the fin 6 of the fourth embodiment, although the first structures 6114 and second structures 6115 of a surrounding portion (not shown) of the foot pocket 61 are also formed on a front end 6111 a and a rear end 6111 b of a dorsum pedis area 6111, two ankle areas 6112 and a heel area 6113, none of the first structures 6114 and the second structures 6115 intersects with a periphery of the foot pocket 61 (i.e., both the first structures 6114 and the second structures 6115 are approximately parallel with the periphery of the foot pocket 61). That is, for the user, the first structures 6114 and the second structures 6115 are alternating concave and convex stripes arranged in a transverse direction rather than longitudinal direction, and the first structures 6114 and the second structures 6115 formed on the front end 6111 a of the dorsum pedis area 6111, the two ankle areas 6112 and the heel area 6113 are approximately arranged in an annular form.

The fifth embodiment of the present invention is also a fin 7. FIGS. 9A and 9B illustrate a top view and a schematic perspective side view of the fin 7. The fin 7 of the fifth embodiment also has a foot pocket 71, two ribs 73, a web portion 75 and a hollow portion 77. The technical features of this embodiment are mostly the same as those of the third embodiment, and thus, the same technical features will not be further described herein.

However, the fin 7 of this embodiment further comprises two connecting components 78 and a flexible belt 79. In detail, the two connecting components 78 are disposed on two sides 717 respectively. In the practical process of manufacturing the fin 7, the two connecting components 78 are integrally formed with the foot pocket 71, the two ribs 73 and the web portion 75 for convenience of the manufacturing process. However, all the aforesaid components do not need to be integrally formed together, and the components may also be formed in groups and then combined together. Alternatively, the fin 7 may be manufactured in the way described in the first embodiment. Each of the connecting components 78 has at least one protrusion 781; and in this embodiment, the one protrusion 781 comprises three protrusions 781.

Two ends of the flexible belt 79 have at least one hole 791 respectively to mate with and connect to the protrusion 781 of the corresponding connecting component 78. In this embodiment, the hole 791 includes one hole 791. The holes 791 of the two ends of the flexible belt 79 are disposed around one of the protrusions 781 on the two sides 717 respectively so that the two ends of the flexible belt 79 are fixed on the two sides 717 of the foot pocket 71. Thus, the fin 7 can be fixed to the user's foot by means of the flexible belt 79 from the back of the user's ankle. The user may insert the holes 791 of the flexible belt 79 into the proper protrusions 781 according to his or her foot perimeter size. If the user has a relatively small foot perimeter size, then he or she can have the holes 791 mate with the protrusions 781 of the corresponding connecting component 78 that are nearer to the front; and if the user has a relatively large foot perimeter size, then he or she can have the holes 791 mate with the protrusions 781 of the corresponding connecting component 78 that are nearer to the back. Furthermore, although both sides can be adjusted, the user may also adjust only one of the sides as needed.

To have the holes 791 of the flexible belt 79 fixedly mate with the corresponding protrusions 781, this embodiment makes each of the protrusions 781 into a hook form that extends and bends forwards to the web portion 75 from the two sides 717 (i.e., as shown by the three back protrusions 781 in FIGS. 9A and 9B, with the forefront protrusion 781 bending around) to prevent the flexible belt 79 from slipping off. According to the above descriptions, other implementations of the protrusions 781 may also be devised by people skilled in the art to surely have the holes 791 of the flexible belt 79 mate with the corresponding protrusions 781. The technical features of this embodiment are mostly the same as those of the third embodiment so that the foot pocket 71 also comprises a heal area 7113 and the flexible belt 79 is passed rearwards by a heel area 7113 from the two sides 717. However, in other embodiments, for example the fin 7 shown in FIG. 9C, the fin 7 also comprises a foot pocket 71, two ribs 73 and a web portion 75. However, the fin 7 does not include a heal area, and the fin 7 merely uses the flexible belt 79 passed rearwards by a rear end of the foot pocket 71 to fix on the two sides 717 of the foot pocket 71. Thus, the fin 7 still can be fixed to the user's foot by means of the flexible belt 79 from the back of the user's ankle.

The protrusions 781 of the fin 7 of the present invention are made of a material such as Ethylene Vinyl Acetate (EVA), Acrylonitrile Butadiene Styrene (ABS), Polycarbonate (PC), Polypropylene (PP), Polyoxymethylene (POM) or a combination thereof; and, those of ordinary skill in the art may use other materials instead, and no limitation is made thereon.

The flexible belt 79 of the fin 7 of the present invention is also made of a soft material such as Thermoplastic Rubber (TPR), Thermoplastic Polyurethane (TPU), Thermoplastic Elastomer (TPE), Polyvinyl Chloride (PVC), Silicone Rubber, Natural Rubber or a combination thereof; and, those of ordinary skill in the art may use other materials instead, and no limitation is made thereon.

The sixth embodiment of the present invention is also a fin 8. FIGS. 10A and 10B, show the top view and side view of the fin 8 respectively. The fin 8 of the sixth embodiment also has a foot pocket 81, two ribs 83, a web portion 85, a hollow portion 87, two connecting components 88 and a flexible belt 89. The technical features of this embodiment are mostly the same as those of the fifth embodiment of the present invention, and thus, the same technical features will not be further described herein.

However, it shall be particularly appreciated that the sixth embodiment differs from the other embodiments mainly in that in the fin 8 of the sixth embodiment, a surrounding portion 811 further comprises a securing ring 8116 disposed on a dorsum pedis area of the foot pocket 81 to surely have holes 891 of the flexible belt 89 fixedly mate with corresponding protrusions 881. The flexible belt 89 is inserted, just like a belt, through the securing ring 8116, and then the holes 891 of two ends of the flexible belt 89 are mated with one of the protrusions 881 on two sides 817 respectively. Thus, the fin 8 can be fixed to the user's foot by means of the flexible belt 89 from the front of the user's ankle. In other implementations of this embodiment, other numbers of securing rings or securing rings disposed at other positions may also be devised by people skilled in the art.

Furthermore, unlike the connecting components 78 of the previous embodiment, the protrusions 881 of the connecting components 88 are each made into a hook form that bends rearwards to a heel area 8113 from the two sides 817 (i.e., as shown by the three back protrusions 881, with an end of the forefront protrusion 881 bending around slightly); and the flexible belt 89 is inserted through the securing ring 8116 to mate with one of the protrusions 881 to prevent the flexible belt 89 from slipping out. According to the above descriptions, other implementations of the protrusions 881 may also be devised by people skilled in the art to have the holes 891 of the flexible belt 89 mate with the corresponding protrusions 881.

In addition, the user may insert the holes 891 of the flexible belt 89 into a proper one of the protrusions 881 according to his or her foot perimeter size. If the user has a relatively small foot perimeter size, then he or she can have the holes 891 mate with the protrusions 881 of the corresponding connecting component 88 that are nearer to the back; and if the user has a relatively large foot perimeter size, then he/she can have the holes 891 with the protrusions 881 of the corresponding connecting component 88 that are nearer to the front. Furthermore, although both sides can be adjusted, the user may also adjust only one of the sides as needed.

According to the descriptions of the above embodiments, people skilled in the art may also devise other similar implementations of the first structures and the second structures. For example, when the first structures and the second structures are long concave and convex straps, the first structures and the second structures may be radially and alternately arranged, arranged in other regular forms, form multiple incontinuous segments of concave and convex long straps, or arranged in other irregular forms. Furthermore, the first structures and the second structures are not limited to the long-strap form. According to the above descriptions, people skilled in the art may also devise other implementations of the protrusions of the connecting components and the holes to have the holes of the flexible belt mate with the corresponding protrusions, and the positions and the numbers of the protrusions and the holes are not merely limited to those described in the aforesaid embodiments.

According to descriptions of the above embodiments, people skilled in the art can devise other implementations, so it is unnecessary for the first structures and the second structures to be formed on the complete surrounding portion as long as there is a difference in thickness.

Because the first structures with a relatively large thickness can provide a stable support and the second structures with a relatively small thickness has a desired stretchability, the user does not need to worry about the size and form of the fin fitting snugly with his or her foot. Also, the fin can be stretched according to different foot forms so that people of all foot forms can wear the fin comfortably. For manufacturers, it is unnecessary to manufacture fins of different sizes in response to various needs, so the cost can be reduced.

The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended. 

1. A fin, comprising: a foot pocket, having a surrounding portion and a base portion for defining a foot receiving space, and the surrounding portion having a plurality of first structures and a plurality of second structures; two ribs, extending forwards from two sides of the foot pocket respectively; and a web portion, being formed between the two ribs, wherein the first structures and the second structures are alternately arranged, and a first thickness of each of the first structures is thicker than a second thickness of each of the second structures.
 2. The fin as claimed in claim 1, wherein the surrounding portion comprises a dorsum pedis area.
 3. The fin as claimed in claim 2, wherein the surrounding portion further comprises two ankle areas and a heel area, and the ankle areas extend from two ends of the dorsum pedis area respectively and connect to the heel area to define the foot receiving space with the base portion.
 4. The fin as claimed in claim 3, wherein the first structures and the second structures are formed on at least one of the dorsum pedis area, the ankle areas or the heel area.
 5. The fin as claimed in claim 3, wherein the dorsum pedis area comprises a front end and a rear end, and the first structures and the second structures are formed on at least one of the front end or the rear end.
 6. The fin as claimed in claim 3, wherein each of the ankle areas has at least one hole.
 7. The fin as claimed in claim 3, wherein a vertical height of the ankle areas and a vertical height of the heel area define an altitude difference therebetween.
 8. The fin as claimed in claim 7, wherein the altitude difference is between 10 mm and 80 mm.
 9. The fin as claimed in claim 5, further comprising a hollow portion formed in front of the front end.
 10. The fin as claimed in claim 1, wherein the first structures and the second structures are alternately disposed along a direction.
 11. The fin as claimed in claim 1, wherein the first structures and the second structures are radially and alternately disposed.
 12. The fin as claimed in claim 1, wherein the first thickness is between 1 mm and 15 mm, the second thickness is between 0.5 mm and 5 mm, and the first thickness is 0.5 mm to 14.5 mm thicker than the second thickness.
 13. The fin as claimed in claim 1, wherein a material of the foot pocket is a soft material selected from Thermoplastic Rubber (TPR), Thermoplastic Polyurethane (TPU), Thermoplastic Elastomer (TPE), Polyvinyl Chloride (PVC), Silicone Rubber, Natural Rubber, Ethylene Vinyl Acetate (EVA) or a combination thereof.
 14. The fin as claimed in claim 1, further comprising two connecting components and a flexible belt, each of the connecting components being disposed on each of the sides of the foot pocket respectively, each of the connecting components having at least one protrusion, two ends of the flexible belt having at least one hole respectively, and the at least one hole mating with and being connected to the at least one protrusion.
 15. The fin as claimed in claim 14, wherein the at least one protrusion comprises a plurality of protrusions, the at least one hole comprises a hole, and one of the protrusions mates with and is connected to the hole.
 16. The fin as claimed in claim 14, wherein the surrounding portion further comprises at least one securing ring, and the flexible belt passes through the at least one securing ring.
 17. The fin as claimed in claim 14, wherein the at least one protrusion extends forwards to the web portion.
 18. The fin as claimed in claim 14, wherein the surrounding portion further comprises a heel area, and the at least one protrusion extends backwards to the heel area.
 19. The fin as claimed in claim 14, wherein a material of the protrusions is selected from Ethylene Vinyl Acetate (EVA), Acrylonitrile Butadiene Styrene (ABS), Polycarbonate (PC), Polypropylene (PP), Polyoxymethylene (POM) and the combination thereof.
 20. The fin as claimed in claim 14, wherein a material of the flexible belt is a soft material selected from Thermoplastic Rubber (TPR), Thermoplastic Polyurethane (TPU), Thermoplastic Elastomer (TPE), Polyvinyl Chloride (PVC), Silicone Rubber, Natural Rubber and a combination thereof. 